Where does “Székelyföld” come from?

Székelyföld (Hungarian) comes from Hungarian Székely, from Hungarian székely — Székely.

Ancestry of “Székelyföld”, step by step

Step	Language	Word	Meaning
1	Hungarian	Székely	—
2	Hungarian	székely	Székely

Székelyföld — Etymology, Origin & Word History | Etymology Explorer